The objective of this study was to investigate the feasibility of treating relapses of multiple sclerosis (MS) at home with oral dexamethasone. Twenty-five out of 28 consecutive patients with MS who presented with a relapse of less than 2 weeks' duration were treated on an open basis with oral dexamethasone 16 mg per day (four divided doses) for 5 consecutive days. After one week, the expanded disability status scale (EDSS) had improved by one or more grades in 88% (22 patients) and after 4 weeks in 92% (23 patients). Treatment was well tolerated. We conclude that a course of oral dexamethasone 16 mg per day shortens the duration of an exacerbation in MS in a similar way as seen after high dose i.v. methylprednisolone. Although a randomized study is needed to test this treatment regimen against i.v. high dose corticosteroids, oral dexamethasone can be used in situations when i.v. therapy is difficult to apply. Copyright 1999 Harcourt Publishers Ltd.